Inkjet printers include serial inkjet printers and line inkjet printers. A serial inkjet printer has a small printhead, and to print alternately executes a main scanning operation of ejecting ink droplets while moving the printhead widthwise to the print medium (in a main scanning direction), and a sub-scanning operation of moving the print medium (or printhead) in a sub-scanning direction intersecting the main scanning direction. A line inkjet printer, however, has a printhead (line head) large enough to eject ink droplets across the full width of the print medium, and when printing ejects ink droplets substantially simultaneously from the printhead across the full width of the print medium while conveying the print medium (or printhead) (see JP-A-2014-184695, for example). A line inkjet printer can print faster than a serial inkjet printer. Note that the ink ejection range of the line head does not necessarily need to cover the full width of all print media on which the line inkjet printer can print.